Centrifugal pumps composed primarily of plastic components

ABSTRACT

A centrifugal pump composed primarily of plastic components. The pump has a wall formed with an inlet through which liquid is sucked into the pump. A rotary impeller is coaxial with the inlet and located closely adjacent to the latter wall. This wall carries a wear-resistant disc which has an exposed surface directed toward and located closely adjacent to the impeller, defining a narrow gap therewith. Part of the wear-resistant disc is embedded in the housing wall, which is made of plastic, in such a way that part of the plastic material of the wall is situtated between the embedded portion of the disc and a plane which contains the exposed surface of the disc.

States atent [191 Aug. 13, 1974 1 CENTRIFUGAL PUMPS COMPOSED PRIMARILYOF PLASTIC CONENTS [22] Filed: Aug. 10, 1972 [21] Appl. No.: 279,375

[52] US. C1 415/197, 415/200, 415/214 [51] Int. Cl. F04d 7/00, F04d 7/02[58] Field of Search 415/197, 200, 214

[56] References Cited UNITED STATES PATENTS 3,685,919 8/1972 Speck eta1. 415/200 FOREIGN PATENTS OR APPLICATIONS 34l,362 l/l93l Great Britain4l5/I97 218,243 l0/l958 Australia 415/197 72,979 4/1960 France 415/197Primary Examiner-Henry F. Raduazo Attorney, Agent, or Firm-Steinberg &Blake 5 7] ABSTRACT A centrifugal pump composed primarily of plasticcomponents. The pump has a wall formed with an inlet through whichliquid is sucked into the pump. A rotary impeller is coaxial with theinlet and located closely adjacent to the latter wall. This wall carriesa wear-resistant disc which has an exposed surface directed toward andlocated closely adjacent to the impeller, defining a narrow gaptherewith. Part of the wear-resistant disc is embedded in the housingwall, which is made of plastic, in such a way that part of the plasticmaterial of the wall is si'tutated between the embedded portion of thedisc and a plane which contains the exposed surface of the disc.

2 Claims, 1 Drawing F igure CENTRIFUGAL PUMPS COMPOSED PRIMARILY OFPLASTIC COMPONENTS BACKGROUND OF THE INVENTION It is already known toconstruct centrifugal pumps with individual housing components made ofplastic. The housing includes a wall formed with a suction inlet throughwhich water or other liquid is sucked into the pump, and locateddirectly next to this inlet is a rotary impeller which is completelyopen at its portion which is directed toward the inlet. Between theimpeller and the wall of the housing which is adjacent the impellerthere is an extremely small gap. The liquid which is pumped, mostlywater, has suspended therein small particles such as, for'example,grains of sand which are drawn through a filter, in the case of a pumpwhich is used to circulate water in a swimming pool. Travel of suchparticles through the gap between the impeller and the housing wallwhich defines the narrow gap therewith results in an intense wear at theimpeller and at the housing wall which defines the narrow gap with theimpeller. This wear can readily be taken care of in the case of theimpeller since the impeller, especially when it is made of plastic, isinexpensive to manufacture and is easily replaced. On the other hand,the housing components are much more expensive to manufacture and muchmore difficult to disassemble. It has therefore become customary tolocate at the housing component which is adjacent the impeller a discwhich is made of a material which has a high resistance to wear. Thefixing of this disc to the housing is brought about in known plasticpump constructions either by bonding or by way of suitable screws.

Experience has shown, however, that this type of fixing of thewear-resistant disc is extremely expensive, the maintenance of thedesired tolerances is not as sured, and the reliability of the fixing ofthewearresistant disc is not very great.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide a pump construction which will avoid theabove drawbacks.

Thus, it is an object of the invention to provide a centrifugal pumpcomposed primarily of plastic components and having a wear-resistantdisc which is mounted in an extremely simple manner while reliablymaintaining the required tolerances and the required fixing of thewear-resistant disc to the housing.

It is furthermore an object of the present invention to provide aconstruction according to which the fixing of the wear-resistant disc tothe housing takes place during molding of that part of the housing whichcarries the disc.

In accordance with the invention, the housing of the pump has a plasticwall formed with a pump inlet through which liquid is sucked into thepump. Directly next to this housing wall is a rotary impeller means. Thelatter housing wall carries immediately adjacent the impeller means awear-resistant disc which has directed toward the impeller means anexposed surface which defines a predetermined narrow gap with the rotaryimpeller means. A portion of the wear-resistant disc is embedded in theplastic material of the housing wall in such a way that part of thelatter plastic material is located between the latter portion of thedisc and a plane which contains the exposed surface of the wearresistantdisc. In this way the disc is reliably fixed to the plastic housingwall.

BRIEF DESCRIPTION OF DRAWING The invention is illustrated by way ofexample in the accompanying drawing which forms part of this applicationand in which one possible embodiment of a centrifugal pump according tothe invention is illustrated in a sectional elevation, the section ofthe'drawing being taken in a plane which contains the axis of theimpeller.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawing, thereis shown therein a centrifugal pump composed primarily of plasticcomponents. Thus, the pump includes: a housing having the suctioncomponent 1 and the pressure component 2 which are made of plastic, byinjection molding, for example. The side of the pressure housingcomponent 2 which is opposite from the suction housing component 1carries an intermediate flange 3 which is removably fixed by suitablebolts or the like to the housing component 2. This intermediate flange 3carries an exterior flange 4 which is removably fixed to theintermediate flange 3 and which carries the motor which drives the pump.The intermediate flange 3 is formed with a central opening through whichthe impeller drive shaft 5 extends, this shaft 5 being driven directlyfrom the motor.

The intermediate flange 3 carries, with a sealed, fluid-tight fit athrust ring 6 which surrounds but does not engage the impeller shaft 5.By way of a key 10, the shaft 5 is fixed with the rotary impeller means9 which rotates together with the shaft .5. A cap nut 11 is threadedonto the free end of the shaft 5 and presses a washer against the rightend surface of the hub of the impeller 9, as viewed in the drawing. Aslidable sealing ring member 7 is situated between the thrust ring 6 andthe impeller 9. This slidable sealing ring component 7 rotates togetherwith the shaft 5. The seal between the thrust ring 6 and the sealinggland 7 is brought about by way of the pressure of a spring 8 which iscoiled about the element 7. In the illustrated example the sealing ring7 is axially stretchable and the spring 8 is situated between andpresses against a pair of outwardly directed annular flanges of thesealing ring 7 so that the spring 8 tends to axially stretch the:sealing ring 7, pressing the latter on the one hand against the rightend surface of the thrust ring 6, as viewed in the drawing, and againstthe left end surface of the hub of the impeller. In the event that thesealing ring 7 is replaced by a component which is not axiallystretchable, the spring 8 presses at its right end, as viewed in thedrawing, against a collar which forms part of the impeller 9.

The inner surface of the flange or wall 3 which is directed toward theimpeller 9 is formed with a radial or spirally curved liquid-guidinggroove 12 which serves to deflect part of the pumped liquid intoengagement with the sealing ring 7, particularly the sealing surfacethereof, so that the sealing ring 7 is continuously cooled by the liquidwhich is pumped.

The component 1 of the pump housing is made of plastic, as was pointedout above, and defines with the impeller means 9 a narrow gap 18. Thepart of the wall 1 which is directed toward the impeller means 9 carriesthe illustrated wear-resistant disc 13 which has an exposed surfacedirected toward the impeller means 9 and defining the gap 18 therewith.

The wear-resistant disc 13 is bonded to the plastic of the housing wall1 by molding the plastic of the wall 1, during the manufacture of thelatter, directly onto that surface of the disc 13 which is directed awayfrom the impeller 9. Thus, during injection molding of the wall 1 thelatter is molded directly onto the disc 13. The disc 13 has a portionembedded in the plastic wall 1 with the latter situated between theembedded portion of the disc 13 and the plane which contains the exposedsurface of the disc 13 which is directed toward the impeller 9 anddefines part of the gap 18. In the illustrated example the embedded partof the disc 13 is formed by its peripheral edge 14. This peripheral edge14 forms part of a cone whose apex is situated in the common axis of theimpeller 9 and the inlet opening which is formed in the wall 1, at theside of the impeller which is opposite from the wall 1. Thus, it will beseen that the peripheral edge 14 tapers so that the surface of disc 13directed away from the impeller has a greater diameter than the surfacethereof which is directed toward the impeller, and thus part of thematerial of the wall 1 is situated between the peripheral edge 14 andthe plane which contains the exposed surface of disc 13 which isdirected toward the impeller 9. In this way an undercut type ofembedding of the disc 13 in the plastic material of the wall 1 isachieved for providing a very reliable fixing of the disc 13 to thewall 1. Thus, when the wall 1 is molded onto the disc 13, the plasticmaterial of the wall 1 flows around and completely embeds the taperedperipheral edge region 14 of the disc 13.

Furthermore, the disc 13 is provided with projections 15 in the form ofbosses or the like, one of which is illustrated in the drawing. Thisprojection is integral with the remainder of the disc and extendstherefrom in a direction away from the impeller 9. During molding of thewall 1, the plastic material thereof also surrounds the projections 15,and in addition to providing a better holding of the disc 13 assembledwith the wall 1, these projections 15 secure the disc 13 against anypossible rotary movement with respect to the housing wall 1.

In order to reliably maintain the gap 18 between the impeller 9, whichis surrounded by the housing component 2, and the wear-resistant disc 13in the wall 1 of a uniform width at all locations, it is required thatthe housing components 1 and 2 be fixed to each other in such a way thatthey will resist any possible distortion. This connection between thehousing components 1 and 2 is brought about in the illustrated example,in accordance with a further feature of the invention, by forming in thehousing component 1, adjacent its periphery, a circular groove 16 whichreceives an elongated cylindrical portion 17 of the housing component 2.This cylindrical portion 17 extends into and fills the groove 16 and isbonded to the housing component 1 either by being welded thereto or by asuitable adhe- SIV.

As pointed out above, it is sufficient to achieve the objectives of theinvention if the plastic of the section housing component 1 duringmanufacture thereof is molded against that surface of the disc 13 whichis directed away from the impeller, with the disc 13 situated directlyin the injection molding form during injection molding of the wall 1.However, as shown in the illustrated example, it is preferred to providethe wearresistant disc 13 with a portion such as its peripheral edge 14and/or the projections 15 which are surrounded by the injection-moldedplastic material, so that not only the projections 15 but also theperipheral edge 14 of the disc 13 achieve a type of hooking of thewear-resistant disc in the plastic material of the wall 1, as a resultof the undercut embedding of part of the disc 13 in the material of thewall 1. If required, the wearresistant disc can also have other types ofprojections which are surrounded by the plastic of the housing wall 1during injection molding thereof.

Experience has shown that fixing of the wearresistant disc to theplastic wall of the housing by gluing, for example, is an unsatisfactorysolution to the problem. Therefore, it is not to be expected that thefixing of the wear-resistant disc by molding of the plastic of thehousing wall directly onto the wear-resistant disc would provide a greatimprovement. Experience has shown, however, that as a result ofinjection molding of the housing wall directly onto the wear-resistantdisc, an outstanding bond and fixing of the wear-resistant disc to theplastic material of the housing wall is achieved. The wear-resistantdisc has substantial rigidity and can be made of a plastic materialwhich is made of a relatively hard wear-resistant composition, or it maybe made of bronze.

The embedding of the tapered peripheral edge of the disc in the materialof the wall 1 further improves the mounting of the wear-resistant disc,and instead of embedding the entire periphery of the disc 13 in the wall1 it is possible also to provide a construction according to which onlypart of the periphery is embedded in the wall 1. The security againstany possible relative rotary movement between the disc 13 and the wall 1is increased by providing the projections 15 which are also embedded inthe plastic material. Furthermore, these projections 15 provide theadded advantage of determining the position of the disc 13 in theinjection mold in a far better manner than is possible if theseprojections were not provided.

It is important to maintain a predetermined gap 18 between the impeller9 and the wall 1, and this maintenance of a gap of predeterminedmagnitude is achieved by fixing the housing components 1 and 2 to eachother in such a way that they cannot become distorted. This maintenanceof the housing components 1 and 2 fixed to each other in such a way thatthey cannot become distorted also reliably maintains the desiredreduction in wear. Thus, the distortion is prevented by theabovedescribed type of tongue-and-groove connection between the housingcomponent 2 and the housing component 1 which is provided by receivingthe cylindrical tongue 17 in the circular groove 16 with welding orgluing of the components 1 and 2 to each other as described above.

What is claimed is:

1. In a centrifugal pump which is adapted to be used for circulatingwater in a swimming pool and which is composed primarily of plasticcomponents, a housing having a wall formed with an inlet through whichliquid is sucked into the pump, rotary impeller means coaxial with saidinlet and located immediately adjacent said wall, the latter carrying awear-resistant disc of substantial rigidity which has an exposed surfacedirected toward said rotary impeller means and defining a narrow gaptherewith, said housing wall being made of plastic molded directly ontosaid disc to be bonded therewith and said disc having a portion embeddedin the plastic of said wall, as a result of the molding of the latteronto said disc, with a part of the plastic of said wall situated betweensaid portion of said disc and a plane which contains said exposedsurface of said disc, so that said disc is reliably fixed to said wall,said portion of said disc being formed by a peripheral edge region ofsaid disc which forms part of a cone whose apex is situated in thecommon axis of said impeller means and inlet at the side of saidimpeller means opposite from said inlet, so that said disc has directedaway from said impeller means a surface of a greater diameter than saidexposed surface and concentric therewith, said surface of said discwhich is of said greater diameter being completely covered by theplastic of said wall and the plastic of said wall also covering thetapered periphery of said disc which is at the side thereof oppositefrom said surface of greater diameter.

2. The combination of claim 1 and wherein said disc carries projectionswhich are directed away from said impeller means and which are alsoembedded in the plastic wall of said housing means. l

1. In a centrifugal pump which is adapted to be used for circulatingwater in a swimming pool and which is composed primarily of plasticcomponents, a housing having a wall formed with an inlet through whichliquid is sucked into the pump, rotary impeller means coaxial with saidinlet and located immediately adjacent said wall, the latter carrying awearresistant disc of substantial rigidity which has an exposed surfacedirected toward said rotary impeller means and defining a narrow gaptherewith, said housing wall being made of plastic molded directly ontosaid disc to be bonded therewith and said disc having a portion embeddedin the plastic of said wall, as a result of the molding of the latteronto said disc, with a part of the plastic of said wall situated betweensaid portion of said disc and a plane which contains said exposedsurface of said disc, so that said disc is reliably fixed to said wall,said portion of said disc being formed by a peripheral edge region ofsaid disc which forms part of a cone whose apex is situated in thecommon axis of said impeller means and inlet at the side of saidimpeller means opposite from said inlet, so that said disc has directedaway from said impeller means a surface of a greater diameter than saidexposed surface and concentric therewith, said surface of said discwhich is of said greater diameter being completely covered by theplastic of said wall and the plastic of said wall also covering thetapered periphery of said disc which is at the side thereof oppositefrom said surface of greater diameter.
 2. The combination of claim 1 andwherein said disc carries Projections which are directed away from saidimpeller means and which are also embedded in the plastic wall of saidhousing means.